1. Field of Invention
This invention relates to a device for remotely injecting an animal with a liquid.
2. Description of the Related Art
Most large animals both wild and domestic are wary of human contact and are, therefore, difficult to capture when capture is necessary for medical treatment or other purposes. For example, in ranch or feedlot operations cattle often must be injected with a drug or treated for disease or injury. When allowed free range cattle become wary and difficult to catch. Capturing a single animal for injection entails many risks including possible injury to the cow, possible injury to the cowboy, and disruption of the herd which may lead to weight loss or injury to other cattle.
In cases where the intent of capture is injection of a drug or other fluid a method of remote injection is preferable to actual physical capture of the animal. In many instances the animal may be approached to a distance sufficient for remote injection without the disruption and risk of injury caused by physical capture.
Several systems for remote injection of animals have been conceived. Generally such systems involve a missile which may be projected toward the animal from a distance by apparatuses such as crossbows, blowguns, and compressed gas guns. Typically these systems include a barrel with a needle assembly at the forward end. The barrel typically contains a primary chamber at the forward end which holds the fluid to be injected. The primary chamber is typically separated from a secondary chamber at the rearward end of the barrel by a plunger or piston which forms a seal. When the primary chamber is charged or loaded the plunger or piston is pushed rearward and held in place by a trigger mechanism. The secondary chamber ordinarily includes some form of potential energy source such as a compressed spring tending to push the plunger or piston forward. Upon impact of the missile with the target animal the trigger mechanism is tripped allowing the piston or plunger to move forward. The potential energy source in the secondary chamber forces the piston or plunger forward and pushes the fluid through the needle assembly and into the animal.
Several inventions embrace the above describe system to some extent and include a variety of trigger mechanisms and sources of potential energy. Some of the inventions include a method of remote retrieval of the missile and some include a barb on the needle assembly which serves to hold the missile in place during the injection process.
U.S. Pat. No. 3,042,406; Gregory (1962) discloses a missile which generally conforms to the system described above. The trigger mechanism is a spring which holds the plunger in a rearward position when the missile is charged. Potential energy is supplied by elastic bands tending to pull the plunger forward. Upon impact the spring is released which allows the elastic bands to pull the plunger forward. The patent also teaches a compressible collar at the front of the missile. Upon impact the collar compresses and after the injection process is complete the collar regains its uncompressed shape and ejects the needle from the animal.
The patent teaches no method of remote retrieval of the missile and no method of holding the missile in place during the injection process.
U.S. Pat. No. 4,106,770; Gray (1978) discloses a projectile which operates in a manner similar to that described above. The trigger mechanism includes clips or "fingers" which hold the plunger in a rearward position when the projectile is charged and a slideable weight. Potential energy is provided in the form of a spring compressed when the missile is charged. Upon impact the slideable weight moves forward releasing the plunger from the clips and allowing the spring to force the plunger forward.
The patent teaches no method of remote retrieval of the missile and no method of holding the missile in place during the injection process.
U.S. Pat. No. 4,121,586; Lawrence et al. (1978) discloses a dart operating in a manner similar to that described above. The trigger mechanism includes a breakable retaining pin which holds the plunger in a rearward position when the dart is charged. Potential energy is supplied in the form of stretched elastic bands which tend to push the plunger forward. Upon impact the retaining pin breaks allowing the elastic bands to push the plunger forward.
The patent teaches no method of remote retrieval of the missile and no method of holding the missile in place during the injection process.
U.S. Pat. No. 4,182,327; Haley (1980) discloses an apparatus which operates in a manner similar to that described above. The trigger mechanism involves a hollow needle assembly. The rearward end of the needle assembly includes a conical surface which forms a seal with a similar conical surface at the front of the barrel when the needle assembly is in a forward position. Upon impact the needle assembly is forced rearward and held in a rearward position by a clip. With the needle assembly in a rearward position ports in the needle assembly are exposed allowing fluid to flow from the primary chamber through the ports into the needle assembly. Potential energy is supplied in the form of a spring which is compressed when the plunger is pushed rearward.
The patent teaches a barb which serves to hold the apparatus in place in the animal during the injection process and also includes a method of remotely retrieving the apparatus.
U.S. Pat. No. 4,863,428; Chevalier (1989) discloses a dart which operates in a manner similar to that describe above. The trigger mechanism includes a cap which is pushed onto the end of the needle assembly after the dart is charged. The cap prevents fluid from flowing through the needle assembly. Upon impact the needle assembly is pushed through the cap exposing the end of the hollow needle. Potential energy is supplied by a spring in the secondary chamber which is compressed when the dart is charged and the plunger forced rearward.
The patent teaches a barb which serves to hold the apparatus in place in the animal during the injection process, but includes no method of remotely retrieving the apparatus.
U.S. Pat. No. 5,202,533; Vandersteen (1993) discloses an apparatus which operates in a manner similar to that described above. The trigger mechanism involves two O-rings. The first O-ring encircles the perimeter of a release member connected to the plunger by a shaft. A second O-ring is seated inside the perimeter of the barrel. The outside diameter of the first O-ring is greater than the inside diameter of the second. When the plunger is pushed rearward the O-ring on the release member is forced passed the second O-ring, but is held in place and prevented from moving forward by the difference in diameters of the O-rings. Upon impact the O-ring on the release member is pushed passed the second O-ring allowing the plunger to move forward. Potential energy is supplied by a spring in the secondary chamber which is compressed when the apparatus is charged and the plunger is forced rearward.
The patent teaches a remote retrieval method and also includes a ferrule on the needle which acts to hold the apparatus in place during the injection process.
Each of the prior art devices is unsatisfactory for many reasons. Each of the devices includes one or more such unsatisfactory aspects which make them unsatisfactory for field use. Other disadvantages may be apparent to persons reasonably knowledgeable in the art.
Those devices lacking a system for remote retrieval largely defeat the purpose of remote injection. If a target animal is missed or more than one animal is to be injected non-remote retrieval is likely to cause disruption and possibly to cause injury to the device, the animals, or the rancher.
Those devices lacking a barb or ferrule to hold the device in place are likely to be ejected from the animal prior to completion of the injection process.
Those devices having a barb or ferrule to hold the device in place during the injection process are likely to cause skin or tissue damage with concurrent possibilities of infection or disease upon impact or ejection of the device.
The trigger mechanisms of the prior art devices are either complicated and difficult and costly to manufacture or subject to failure on a relatively consistent basis.
The source of potential energy in many of the prior art devices are unnecessarily complicated, must be replaced prior to each injection, or include parts subject to wear and failure.
In may cases loading or charging of prior art devices is unnecessarily complicated and time consuming and often involves at least partial dismantling and reassembly of the device.